Jan., 1037
PROPERTIES OF SPRUCE LIGNINEXTRACTED WITH FORMIC ACID
The writers wish to thank Dr. Douglas G. Hill for suggestions on the kinetics of these reactions. Summary
1. The rates of decomposition of the sodium salts of a series of substituted bromobenzamides have been measured a t 30'. 2 . The rates of decomposition of the sodium salts of bromobenzamide and of m-chloro- and pmethylbromobenzamides have been measured at two or three temperatures and their heats of activation calculated. 3. It has been found that the relative rates of decomposition of certain meta and para substituted bromobenzamides a t 30°, and presumably their relative ease of rearrangement in the pres-
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ence of alkali, are inversely related to the dissociation constants of the corresponding carboxylic acids. 4. These results are considered to be in agreement with the hypothesis that the ease of rearrangement of a bromoamide in the presence of alkali is dependent upon the ease of release of bromide ion from the negative ion of the alkali salt. 5 . It has been found that in the presence of excess alkali a t 30°, p-nitrobromobenzamide gives approximately as much p-nitrobenzoic acid by hydrolysis as p-nitroaniline by rearrangement ; at 96-100°,however, a 90% yield of p-nitroaniline is obtained. DURHAM, N. C.
INDUSTRIAL AND CELLULOSE CHEMISTRY,
RECEIVED AUGUST12, 1936
MCGILLUNIVERSITY]
Studies on Lignin and Related Compounds. XXVI, The Properties of Spruce Lignin Extracted with Formic Acid BY GEORGEF. WRIGHTAND HAROLD HIBBERT The recent publications by Freudenberg and co-workers' and by Staudinger and Dreher,2 in which they describe the extraction of spruce wood meal with formic acid, anticipate a current investigation in this Laboratory. Although this study is not yet complete it seems advisable to present a preliminary account of the work. Considerable doubt exists as to the reliability of any known extraction process for isolating unchanged lignin from wood, and it seems preferable to consider an extractant as the first reagent in a series of reactions intended to prove structure. As one of a series of such extractants, so regarded, it has been found that boiling formic acid removes from resin- and soluble-carbohydrate-free spruce wood meal 17y0of its weight in the form of methoxyl-containing material. Because of partial demethoxylation this process yields lignins of comparatively low methoxyl content (12-1473 but it possesses the advantages of: (a) rapidity and convenience of extraction, and (b) isolation of extracts readily soluble in many organic solvents. Thanks to this ease of solubility, it has been found possible to effect a separation of the isolated lignin into five fractions by precipitation of chloroform, acetone and
aqueous acetone solutions into ether and also petroleum ether (Table I). This fractionation is undoubtedly incomplete ; indeed, subsequent experiments show that the fractions are still complex. Nevertheless, examination of these partially separated products shows a definite trend in chemical and physical properties undoubtedly characteristic of the individual substances that comprise the isolated mixture called lignin. The behavior of two functional groups has been examined in this study, namely, (a) reactions of the hydroxyl and (b) reactions of the carbonyl group. The suitable solubility of formic acid lignin has permitted the use of the Grignard machine3 for simultaneous determination of both groups. These analyses have been supplemented by appropriate methoxylations and tosylations. The results (Table I) show two interesting facts: (i) the native lignins contain small amounts of non-enolizable carbonyl groups; (ii) the more soluble, and therefore simplest, fractions, have higher hydroxyl and lower methoxyl values than their more complex, insoluble analogs. This decrease in hydroxyl value with decreasing solubility suggests that increasing aggregation of
(1) Freudenberg, Janson. Rnapf and Kaag, Bcr., 69, 1415 (1936). (2) Staudinger and Dreher,
